Overview

Can nitrogen models increase net revenues when compared to traditional N management rates? What about when compared to an N rate recommendation from the Corn N Rate Calculator? Several Midwestern land grant universities conducted a study to test this theory.

The nitrogen management model produced the lowest net revenues. These net revenues were $21. They were $27/acre lower than the net revenues produced by the growers’ traditional N management rates and the N rate recommended by the Corn N Rate Calculator.

While nitrogen management models may become more accurate with time, this study suggests that for now growers should proceed with caution before adopting N management models for wide-scale use.

Brief Introduction

Within the last few years, nitrogen management models seem to be all the rage. DuPont Pioneer promotes Encira Yield Nitrogen, Monsanto has Climate-N, and Agronomic Technology offers Adapt-N. This is a short list of the Big 3, but there are still the droves of Silicon Valley start-ups promising to solve all our nitrogen management woes.

The idea behind these N models is stellar: use less fertilizer N in years with low nitrogen loss conditions and more fertilizer N in years when more N loss has occurred. Potentially, this could reduce N pollution, save on fertilizer N costs, or increase yields in years when more fertilizer nitrogen is required.

This is, of course, the utopia for which the agricultural industry has been searching.

I am sure the aforementioned corporations have hired the best in the business to take on such a monumental task and that they are using the most advanced statistical models known to man. However, Mother Nature—and the complexities of the nitrogen cycle—will put up a formidable fight.

I can only hope that they have been successful. Answering these complex questions would be a win for farmers, for the agricultural industry, and for the general public. But are these nitrogen management models currently being sold to farmers ready for the “big league?” Can these nitrogen management models help farmers make better business decisions as soon as the 2017 crop season? The answer to that question still isn’t clear.

This past crop season, Liqui-Grow implemented experiments to give both us and our customers some clearer answers to this important question.

Applied Questions

Can a nitrogen management model recommend an N rate that results in net profit gains compared to the Corn Nitrogen Rate Calculator developed by several Midwestern land grant universities?

Answering the Applied Questions

In southeast Iowa, nitrogen fertilizer rates ranging from 0-to-250 lbs of N/acre were applied to three different farmers’ fields. It was applied in approximately 50 lbs increments. In each of these three fields, these nitrogen rates were replicated 3 times. Soybeans were the previous crop for each field. Each N rate plot was 30 ft wide and approximately 300 ft long.

Most of the nitrogen was applied at the V-7 growth stage, dribbled on the soil surface as liquid UAN 32%. At each of these fields, the soils were highly productive, prairie derived mollisols with OM ranging from 3.3-to-3.8%.

At the request of the developer, the specific nitrogen model used will remain anonymous. It did, however, come from one of the Big 3.

The profitability from any N rate (or any N recommendation system) can be calculated by applying a wide range of N rates, as we did in these studies. Of course, this depends on the yield that any given N rate produced and the amount of nitrogen it took to produce that yield.

For the economic calculations, $0.39/pound of N was used. The price for a bushel of corn was assumed to be $3.50.

How Did the N Recommendation Systems Compare?

In the interest of being short and sweet, I will only discuss what happened on average across these three different trials. Nevertheless, I have included the results from each of the three locations in Table 1.

Therefore, on average, these three growers typically apply 170 lbs of N/ac when corn follows soybeans. The Nitrogen Rate Calculator, developed by several Midwestern land grant universities, recommended 149 lbs of N/ac, and the N model recommended 136 lbs of N/ac.

In spite of the growers applying 21 more lbs of N/ac than the N Rate Calculator recommendation, the yields between these two N rates were nearly identical. The grower-chosen N rate produced a yield of 230.4 bu/ac and the N Rate Calculator recommendation produced a yield of 229.6 bu/ac. The N model, however, recommends applying 34 and 13 less lbs of N/ac than the grower selected N rate and the N Rate Calculator recommendation. Therefore, the N model recommendation produced approximately 10 fewer bu of corn/ac than either the grower-selected N rate or the N Rate Calculator recommendation (Figure 1).​

The N model recommendations reduced the N cost by a few dollars/acre. However, the lost yield meant that the N model had the lowest net revenue, at $719/acre. The grower-selected N rate and the N Rate Calculator recommendations followed, producing net revenues of $740 and $746/acre.

Results

So, are these N models ready for the “big league?”

With the current commodity climate, I think most farmers will find it hard to gut an extra $27/acre, not to mention access to these N models is not free. No doubt, these N models will likely get more accurate with time. While that happens, however, this small investigation that evaluated only one of these N models would suggest that growers should proceed with caution.

Liqui-Grow will likely continue to evaluate these N management models, so stay tuned for further updates next fall.

Table 1.

Figure 1.

Nitrogen rates and corn yields at three different southeast Iowa locations in the growing season of 2016. Round markers represent the grower-selected N rates. Triangle markers represent the N rates prescribed by a nitrogen management model.